Pacific Northwest Legend
American Indians in the Pacific Northwest often refer to the buttercup as the "Coyote Eye" flower. Storytellers speak of a silly coyote that was using his eyeballs to play catch. Unfortunately, an eagle caught them. The then-blind coyote made some new eyes from the buttercup flower.
The Butter Game
In various locales, including parts of England and New Zealand, a buttercup held under your chin determined whether you liked butter or not. If your skin showed a yellow reflection, the answer was yes. This is a children's game, but one that made it into buttercup lore.